1. Technical Field
The present disclosure generally pertains to wireless communications and, more particularly, to a method for formatting and transmitting an aggregate physical layer protocol data unit (PPDU) in a wireless communications system.
2. Description of the Related Art
Interest in unlicensed 60 GHz millimeter wave (mmW) networks is increasing. wireless Hi-Definition (HD) technology is the first 60 GHz mmW industry standard, which enables multi-gigabit wireless streaming of high-definition audio, video and data among consumer electronics, personal computer and portable products. Another multi-gigabit wireless communications technology operating over the 60 GHz mmW frequency band is WiGig technology, which has been standardized by the Institute of Electrical and Electronic Engineers (IEEE) as the IEEE 802.11ad standard (see IEEE 802.11ad-2012).
The WiGig technology supplements and extends the IEEE 802.11 media access control (MAC) layer and is backward compatible with the IEEE 802.11 wireless local area network (WLAN) standard. The WiGig MAC supports a centralized network architecture such as an infrastructure basic service set (BSS) or a personal BSS (PBSS), where only the central coordinator, e.g., an access point (AP) or personal BSS control point (PCP), transmits beacons to synchronize all stations (STAs) in the network. Rather than other IEEE 802.11 WLAN technologies operating over 2.4 GHz or 5 GHz frequency band, the WiGig technology makes extensive use of BF (beamforming) to achieve directional transmissions.
Due to a standard bandwidth of 2.16 GHz, the WiGig technology is able to offer a physical layer (PHY) data rate of up to 6.7 Gbps. The WiGig PHY supports both single carrier (SC) modulation and orthogonal frequency division multiplexing (OFDM) modulation. For the purpose of increasing transmission efficiency, the WiGig PHY also supports “aggregate PPDU”. In the context of SC modulation, the aggregate PPDU is a sequence of two or more SC PPDUs transmitted without inter-frame spacing (IFS), preamble and separation between PPDU transmissions.
A prevailing application of the WiGig technology is a cable replacement for wired digital interface. For example, the WiGig technology can be used to implement a wireless Universal Serial Bus (USB) link for instant synchronization between smart phones or tablets or a wireless High-Definition Multimedia Interface (HDMI) link for video streaming. The state-of-the-art wired digital interfaces (e.g., USB 3.5 and HDMI 1.3) enable data rates up to tens of Gbps and therefore the WiGig technology also needs to be evolved to match them. Techniques for supporting multiple input multiple output (MIMO) transmission with variable bandwidth while maintaining backward compatibility with existing (i.e., legacy) WiGig devices would be desirable for Next Generation 60 GHz (NG60) WiGig to achieve PHY data rates up to tens of Gbps.
In order to keep backward compatibility with legacy WiGig devices, the NG60 WiGig shall be able to support both legacy format (LF) PPDUs, defined in IEEE 802.11ad, with a standard bandwidth, and mixed format (MF) PPDUs with capability of accommodating MIMO transmission with variable bandwidth. A non-limiting embodiment contributes to providing a transmission format and a transmission method of aggregate MF PPDU in an efficient way such that transmission efficiency can be maximized.